1. Field of the Invention
The present invention relates to a driver, and particularly to, for example, a driver that allows reduction in size of a lens driving portion.
2. Description of the Related Art
FIG. 1 shows the configuration of an exemplary driver of related art. A driver 10 shown in FIG. 1 includes a lens carrier 11, a housing 12, a hook 13, a wire 14, and electrodes 15. The lens carrier 11 is accommodated in the housing 12 in such a way that the lens carrier 11 can move upward and downward relative to the housing 12. The hook 13 is disposed on part of the lens carrier 11 and protrudes through a side surface (outer side) of the housing 12.
The wire 14 is hooked on the hook 13. The wire 14 is disposed along at least two sides of the side surface of the housing 12. An electrode 15 is provided at one end of the wire 14, and an electrode 16 is provided at the other end of the wire 14. The wire 14 is made of a shape memory alloy. When a current is conducted from the electrode 15 to the electrode 16 or vice versa and the temperature of the wire 14 rises, the wire 14 made of a shape memory alloy decreases in length. When the length of the wire 14 decreases, the hook 13 on which the wire 14 is hooked is lifted relative to the housing 12.
Since the hook 13 is integrated with the lens carrier 11, the hook 13 lifted relative to the housing 12 lifts the lens carrier 11 relative to the housing 12. In this way, the lens carrier 11 is driven. Conversely, when the current flowing through the wire 14 is terminated, the temperature thereof lowers and the length thereof increases. When the length of the wire 14 increases (returns back to its original length), the hook 13 and hence the lens carrier 11 are lowered.
A lens barrel (not shown) that holds a lens fits into the lens carrier 11. Driving the lens carrier 11 in the way described above therefore changes the position of the lens held in the lens barrel and hence the focal distance is adjusted. That is, autofocusing (AF) is performed (see WO 2008/099156A2, for example).